The invention pertains to shoes, especially athletic shoes and in particular running shoes. Athletic shoes are increasingly becoming high-tech products, since both the manufacturer and the user of these shoes have extremely high expectations regarding quality and effectiveness, not only concerning the materials used, but especially with respect to the positive effects on the running process and protection of the feet while running. The result of this is that such shoes are designed with a view toward minimizing the strain on the feet and legs.
One object of the invention is to design the soles of such shoes so as to actively cushion the strains that arise while running, such as jolts, countering them by adapted damping properties to cushion their effect.
Piezo-electric materials can convert mechanical energy into electrical energy and vice versa. Mechanical stress causes a charge transfer in these materials, which can be tapped as electrical voltage (piezo effect). On the other hand, the dimensions of these materials changes under the influence of an electrical field (inverse piezo effect). Known piezo-electric materials are, for example, piezo ceramics and piezo-electric PVDF (polyvinylidenefluoride) foils.
Electro-rheological fluids have as a base material an oil in which fine particles float dispersed. This base material determines the base viscosity. When an electric field is created, the particles form chains, the length of which is dependent on the created electric field. Therefore, the viscosity of electro-rheological fluids changes in dependence on the created electric field.